Stenosis is a narrowing or constriction of a duct or canal. A variety of disease processes, such as atherosclerotic lesions, immunological reactions, congenital abnormalities, and the like, can lead to stenosis of arteries or ducts. In the case of stenosis of a coronary artery, this typically leads to myocardial ischema.
Atherosclerosis, also known as arteriosclerosis, is a common human ailment arising from the deposition of fat-like substances, referred to as atheroma or plaque, on the walls of blood vessels. Such deposits occur both in peripheral blood vessels that feed the limbs of the body and in coronary blood vessels that feed the heart. When deposits accumulate in localized regions of a blood vessel, the regions become stenosed, blood flow is restricted, and the person's health is at serious risk.
Numerous approaches using catheters for reducing and removing such stenotic deposits have been proposed, including balloon angioplasty, where a balloon-tipped catheter is used to dilate the stenosed region, atherectomy, where a blade or other cutting element is used to sever and remove stenotic material, and laser angioplasty, where laser energy is used to ablate at least a portion of the stenotic material.
Several different types of entirely disposable dilatation catheters are currently employed and may be generally classified based upon their interaction with a guidewire. Although these disposable catheter designs have proven effective under a variety of conditions, their disposability and specific functionality limit the capacity of the surgeon to adapt to changing or unexpected situations. This may increase the costs associated with their use as several different catheters may be necessary to accomplish a simple procedure. For example, it is often necessary to exchange entire catheters during angioplasty procedures. The catheter exchange may be required for any one of several reasons including catheter balloon malfunction, the inability of the specific balloon size to adequately dilate the vascular stenoses, or the need to insert an additional device to remove vascular material. In each of these situations the original dilatation catheter must be removed and a new catheter inserted. It is estimated that about half of the angioplasty procedures require the use of more than one dilatation catheter. Presently, all of the catheters used during such procedures are discarded after a single use.
For these and other reasons, re-useable catheter designs are desired of the type in which the catheter permits uncomplicated modification of components and catheter configuration. Although some "rapid exchange" catheters have been designed to allow for a reusable proximal end combined with a disposable distal end by employing a "locking mechanism," these locking mechanisms are sometimes deficient. For example, U.S. Pat. No. 5,549,554 relates to catheter having separable reusable components, and provides one or more releasable connectors for connecting distal portions to a central body instrument portion. Although the substitution or modification of catheter components is possible through the releasable connectors, the connectors include only a single locking mechanism. Failure of that single mechanism during a procedure may have adverse consequences.
Additionally, a locking mechanism described in U. S. Pat. No. 4,792,163, relates to a secondary safety clamp for a medical tube coupling. The secondary safety clamp may prevent accidental separation of a pair of connected tubular members of a sliding member. The secondary safety clamp is an integrally molded piece defining a toothed rack plus a retention member made up of a pair of jaws between which there may be retained a parenteral solution administration set. Although the secondary safety clamp may be suitable for applications relating to medical tube couplings, the secondary clamp affords little flexibility for application in a catheter.